i doubt 1.3 litre to 1.8 litre cars will loose value . Here in pakistan prices increase for every product no matter wht the reason.
apart from that 1.3 litre cars now coming with efi with advanced ecu are pretty good when it comes to feul efficeny .
cng is merely an overstated fuel option. the amount you save on the cng /petrol difference is obviously compromised to other factores including but not limited to responsive drive , higher wear and tear of the engine. etc.
if you drive practically and carefully on well planned routes you are bound to get the job done in petrol as opposed to random unplanned visits.
i have never installed any cng in my 3 cars which i own , cuore , mehran and charade . my cuore is a 2004 model , mehran is 2010 and charade is oct 1986 import been with us from day one. even today my charade gives me 13-14 km per litre MASHALLAH with out ac depending on my gear shift and acceleration habits. On the other hand my cousin is equally happy with his stick shift 2005 petrol driven honda city which gives better average then my charade so small cars dont always win. Theres another case of another cousin of mine who is frustrated over the average of his 2007 old shape altis which guzzels 6-8 litre per km.
to stick back to the topic . there really is no proper solution nor do we have any institution or body that regulates , monitors and balances a price check on car categories may it be in 1.3 litre or 800 cc. nor is there any fair value cap on used cars .pricing is going haywire by the day and consumers stand a fat chance of getting a decent car in their budget. our driving habits are a true reflection to our feul consumption keep in mind other factors such as traffic load , road condition etc.
